Certain types of machinery employ a single operator but are equipped to perform at least two, and perhaps more, separate functions. These functions may be for the same overall purpose, e.g. the fabrication of a part, construction of a building, or installation of an underground pipeline but each function of the machine is employed for a different purpose to achieve the overall end. Such machines often have different items of functional equipment disposed at different locations thereon with the operator selecting appropriate controls by changing body position, often by moving from position to position in a swivel-type operator seat. To prevent inadvertent operation of the actuating controls for an item of machine equipment which is not then in use, there is a need for a control device which permits the operation of each of the various equipment items according to the position of the operator's seat. While this invention will have application for multiple function machines generally, it is described particularly with respect to an item of construction machinery.
Excavator vehicles, commonly known as "mechanical shovels", are known which include two sets of earth-moving equipment, both of which are hydraulically controlled from a single control position. In general, these sets of equipment are disposed at opposite longitudinal ends of the vehicle chassis, which is also provided with driving and/or steerable wheels. One of these equipments, namely a digger or backhoe is used in particular for digging trenches, and the vehicle must be held in a stationary position in order for said equipment to be used. In contrast, the equipment at the other end, namely a loader or shovel per se requires the operator to drive the vehicle while it is in use since materials picked up in the shovel are subsequently tipped into a truck for removal.
The control position on the vehicle is therefore equipped with two groups of controls, each corresponding to one of the sets of equipment, and the operator sits on a swivelling seat mounted on a platform of the vehicle.
In each of its extreme positions, the swivelling seat gives the operator easy access to the corresponding group of controls, and in particular the operator has access to the vehicle steering wheel when the shovel is in use. When using the shovel, the shovel equipment must be capable of being controlled by one hand only so as to leave the other hand free to steer the vehicle.
It is also recalled that in this type of vehicle the various elements constituting either of the sets of equipment are actuated by means of at least one hydraulic actuator under the control of a control valve which is in turn servo-controlled to the position of a knob disposed within reach of the operator when sitting in the control position.
The term "knob" is used herein to designate any kind of manually-operated lever, handle, pushbutton, etc. It is also used to cover a set of such devices, and a typical example would be in the form of a "joystick" providing independent positive and negative control effects for forward and reverse movement of the stick and for left and right movement of the stick.
Other excavator vehicles, which may be referred to as "mechanical diggers", have a turret supporting a single set of earth-moving equipment, with the turret being pivotally mounted on a chassis provided with displacement means, e.g. wheels or crawler tracks. In this case, the vehicle control position is disposed on the pivoting turret and the operator generally has remote-control knobs both for controlling the earth-moving equipment and for controlling vehicle displacement.